1. Field of the Invention
The present invention relates generally to devices used to produce extruded products and particularly to devices that are attached to extruders to make the operation thereof more efficient and convenient and devices that allow for locking and a quick change over of devices attached to extruders.
2. Description of Related Art
Extruders for making food products generally operate at relatively high temperatures that cook the products during the extrusion process. During such a process, pressures as high as 300 to 800 psi build up in the barrel of the extruder. Such an extruder is often referred to as an extruder-cooker. When the extruder-cooker has to be shut down, for example, for maintenance or a change over at the end of an operation, the high pressure needs to be relieved safely before performing any other activity on the extruder-cooker, such as die assembly or screw removal. Currently, the methods used to safely relieve the high pressure involve slowly dissipating the pressure over time. This method helps avoid injury to operators from exploding debris, such as loose parts or product, for example, if the extruder is opened to quickly at the end of an operation.
Attempts to solve this problem have been made but have not been acceptable. For example, reference WO 2004/01970 A2 discloses a back pressure valve that is positioned directly in the material flow path. But such a valve is prone to unanticipated variations in the density of the product and to material backing up and plugging of the extruder. In another example, U.S. Pat. No. 4,984,977 discloses a device that may be moved in or out of the flow path of the product. This also risks plugging and as well as trapping material, which presents sanitation and cross contamination issues. In yet another example, U.S. Pat. No. 5,238,385 discloses a Y-Valve Assembly that relieves pressure by diverting the material flow. However, it extends the extruder foot print and requires additional product removal equipment, which is costly and reduces flexibility for incorporating additional processing steps, such as co-extrusion.
Also, in a typical food extrusion process, one or more assemblies or sub-assemblies are attached to the exit end of the extruder to create products with desired characteristics. These assemblies and sub-assemblies may serve, for example, to vary density of a product; expand the product; shape and cut the product e.g., into kibbles; or co-extrude different-colored or textured products. The weight of each of these assemblies and sub-assemblies may vary from approximately 120 lbs to as much as 300 lbs. Some assemblies or sub-assemblies may be fastened to the extruder body or to each other, for example, by bolts or bolts and nuts. Another method uses heavy clamps (50 to 120 lbs) that are locked by bolts and nuts.
Attaching the heavy assemblies and sub-assemblies to the extruder and detaching them from the extruder is time consuming and requires heavy lifting equipment. Often, multiple personnel are needed to complete operations requiring removal, replacing, or adding such devices to the extrusion line. Due to the large number of bolts, there is frequent stripping of bolts leading to high replacement costs. Further, changing such hot, wet and heavy parts creates a high-risk environment for injuries, such as back injuries or injuries caused by, for example, slippage and dropping of heavy parts on fingers or toes of the personnel involved.
There is, therefore, a need for new devices and methods for overcoming these limitations and problems. The present invention provides a solution to these problems and overcome the limitations inherent in current devices.